llvm-project

9e306ad4 - [clang] Remove intrusive reference count from `DiagnosticOptions` (#139584)

[clang] Remove intrusive reference count from `DiagnosticOptions` (#139584) The `DiagnosticOptions` class is currently intrusively reference-counted, which makes reasoning about its lifetime very difficult in some cases. For example, `CompilerInvocation` owns the `DiagnosticOptions` instance (wrapped in `llvm::IntrusiveRefCntPtr`) and only exposes an accessor returning `DiagnosticOptions &`. One would think this gives `CompilerInvocation` exclusive ownership of the object, but that's not the case: ```c++ void shareOwnership(CompilerInvocation &CI) { llvm::IntrusiveRefCntPtr<DiagnosticOptions> CoOwner = &CI.getDiagnosticOptions(); // ... } ``` This is a perfectly valid pattern that is being actually used in the codebase. I would like to ensure the ownership of `DiagnosticOptions` by `CompilerInvocation` is guaranteed to be exclusive. This can be leveraged for a copy-on-write optimization later on. This PR changes usages of `DiagnosticOptions` across `clang`, `clang-tools-extra` and `lldb` to not be intrusively reference-counted.